First, a little clarification:
- You do not have to wait for a weapon's cooldown cycle to fire again to avoid heat scale. The amount of time you have to wait is 0.5 seconds.
- The heat scale is a curve. The multiplier provided in the previous chart move that curve up and down on a graph (which will be detailed below).

Heat Scale - The Maths:
The numbers you really want:

Weapons Fired

0-1

2

3

4

5

6

7

8

9

10

11

12

Heat Scale

0.00

0.08

0.18

0.30

0.45

0.60

0.80

1.10

1.50

2.00

3.00

5.00

Weapon System

Max Alpha

Multiplier

PPC

2

7.0

ERPPC

2

4.5

LRM-20

2

2.8

LRM-15

2

2.8

LRM-10

2

2.8

Large Laser

2

2.8

ER Large Laser

2

2.8

Large Pulse Laser

2

2.8

Medium Laser

6

1.0

AC/2

3

1.0

AC/20

1

24

SRM-2

4

1.0

SSRM-2

4

1.0

SRM-4

4

1

SRM-6

3

1.0

Base Heat Scale Graph:

Case Study - 4 PPC Stalker:

SCENARIO 1
Player fires 2 PPCs.
Player recieves 0.00 heat penalty as Max Free Alpha is set to 2.